(i) Field of the Invention
The present invention relates to a sheet accumulation processing device for accumulating and discharging sheets or a sheet bunch continuously fed from a copying machine, a printer or another image forming device onto a predetermined accumulating tray, especially to a shielding device of an opening formed in a device surface for conveying sheets in a transverse direction and piling the sheets on an accumulating tray.
(ii) Description of the Related Art
In many cases, a rotating roller usually constituted of a drive roller and a free roller engaged with the drive roller to dependently rotate is used in a discharge mechanism for discharging sheets with images formed thereon from a sheet discharge port of an image forming device to a sheet discharge tray. The sheet discharge tray is inclined and attached to the image forming device below, and the sheets discharged one by one are accumulated on the tray while ends of the sheets are aligned with a positioning/matching vertical wall of the image forming device. Furthermore, in an image forming device in which plural sheet discharge trays are provided and sheets can be discharged to an optional sheet discharge tray, when the sheet discharge tray loaded with plural sheets vertically passes the sheet discharge port of the image forming device, the sheets are dropped or narrowed toward the sheet discharge port, thereby disadvantageously jamming the sheets and disturbing matched or superimposed conditions of the sheets, because the sheet discharge device is inclined as aforementioned. To prevent this and other problems, there is provided a shutter device having a drive mechanism for shielding the sheet discharge port at least while the sheet discharge port is vertically moved.
Recently, in a sheet accumulation processing device, instead of discharging the sheets with images formed thereon from the image forming device as they are to the sheet discharge tray as aforementioned, after superimposed end faces of the predetermined number of stacked or gathered sheets are matched, stapling, punching or another processing is performed. The processed sheet bunch can be transferred to an adjoining sheet accumulation processing device, and discharged to a predetermined sheet accumulating tray.
In order to provide a shielding means having a conventional drive mechanism, for example, a motor as a drive device, a drive force conducting belt, a shutter member operatively interconnected to the belt, a shutter position detector and a control device are required for constituting a shielding device. Therefore, costs of these constituting members and a space for arranging the constituting members in a device housing need to be secured. Additionally, the opening/closing of the shutter member needs to be controlled synchronously when a sheet holding means is protruded/retreated into or out of the housing at a high speed. Therefore, reliability would be deteriorated after a long use.
Additionally, even when an opening is provided with some shielding means like in the conventional art, whether intentionally or not, people hands or articles are inserted or entered via the opening into the device while the sheet holding means is inoperative or on standby. In this case, not only device troubles but also safety problems still remain unsolved.